The present book contains the original papers and essential points of the general discussion of a meeting organized in a series of tri-annual conferences, initiated by Dr. R. Plomp with the meeting in Driebergen, The Netherlands, 1969. These symposia have tried to bring toether people from extreme fields in auditory research and to amalgamate their recent findings. This series of conferences has proven to be most successful and has attracted much attention by scientists in auditory research. The organizers have tried to maintain the character of the meeting with em­ phasis on discussion by precirculation of the full text of the papers and by re­ stricting the number of active contributions. Unfortunately, this forced us to reject a great number of submitted papers - in selection we attempted to compose a fair survey of certain fields of auditory research but leave others untreated. Because of the same reason the number of invited review papers had to be limited to three. The reader may decide whether or not this selection was adequate. We thank all those participants who attended the meeting inspite of the rejection of their paper. The authors have been responsible for text and typing of their manuscripts. The editors have not attempted to standardize the spelling.